1. Field of the Invention
The present invention relates to crystallized glass articles having surface patterns imparting to them an appearance such as granite, marble or other natural stones which are adaptable for use as heat resistant, incombustible ornamental wall materials for buildings and the like, and in particular, to such crystallized glass articles having a desired color or colors.
2. Description of the Prior Art
As substitution of natural marble for ornamental building materials, crystallized glass articles have been proposed which have great mechanical strength, excellent heat resistance and excellent efflorescence resistance.
U.S. Pat. No. 3,761,235 (Reference 1) discloses crystallized glass articles having marble-like appearance. The crystallized glass article is produced by heat-treating a crystallizable CaO-Al.sub.2 O.sub.3 -SiO.sub.2 glass, which essentially consists of 15-40 wt % CaO, 3-35 wt % Al.sub.2 O.sub.3, and 40-75 wt % SiO.sub.2.
U.S. Pat. No. 3,964,917 (Reference 2) discloses another crystallized glass articles which is also provided with marble-like appearance. The crystallized glass is produced by heat treating a crystallizable CaO-Al.sub.2 O.sub.3 -SiO.sub.2 -ZnO glass after shaping the glass into a desired shape. The crystallizable CaO-Al.sub.2 O.sub.3 -SiO.sub.2 -ZnO glass essentially consists of 50-65 wt % SiO.sub.2, 3-13 wt % Al.sub.2 O.sub.3, 15-25 wt % CaO, 2-10 wt % ZnO.
U.S. Pat. No. 3,955,989 (Reference 3) discloses a crystallized glass article having a surface pattern like granite, marble or other natural stones which is formed by heat-treatment of collected small crystallizable glass masses. Each of the small masses precipitates needle-like .beta.-wollastonite crystals by the heat-treatment which extend from the surface of the small mass into the interior in a direction generally perpendicular to the surface of the small mass. Therefore, the surface pattern is defined by the small masses forming the surface layer. Reference 3 also discloses a crystallized glass article having a beautiful colored pattern by spraying or applying a solution containing coloring ions onto the collected small masses prior to the heat-treatment. The coloring ions diffuse into the small masses so that the article is colored. However, the article has only a light color. That is, it is impossible to produce an article having a bright colored or a high contrast colored pattern.